'\" te
.\"  Copyright 1989 AT&T
.\" Copyright (c) 1995, Sun Microsystems, Inc.  All Rights Reserved
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
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.TH SEGMAP 9E "Jan 14, 1997"
.SH NAME
segmap \- map device memory into user space
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/vm.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>



\fBint prefix\fR\fBsegmap\fR(\fBdev_t\fR \fIdev\fR, \fBoff_t\fR \fIoff\fR, \fBstruct as *\fR\fIasp\fR, \fBcaddr_t *\fR\fIaddrp\fR,
     \fBoff_t\fR \fIlen\fR, \fBunsigned int\fR \fIprot\fR, \fBunsigned int\fR \fImaxprot\fR, \fBunsigned int\fR \fIflags\fR,
     \fBcred_t *\fR\fIcred_p\fR);
.fi

.SH INTERFACE LEVEL
.sp
.LP
Architecture independent level 2 (DKI only).
.SH ARGUMENTS
.sp
.ne 2
.na
\fB\fIdev\fR \fR
.ad
.RS 12n
Device whose memory is to be mapped.
.RE

.sp
.ne 2
.na
\fB\fIoff\fR \fR
.ad
.RS 12n
Offset within device memory at which mapping begins.
.RE

.sp
.ne 2
.na
\fB\fIasp\fR \fR
.ad
.RS 12n
Pointer to the address space into which the device memory should be mapped.
.RE

.sp
.ne 2
.na
\fB\fIaddrp\fR \fR
.ad
.RS 12n
Pointer to the address in the address space to which the device memory should
be mapped.
.RE

.sp
.ne 2
.na
\fB\fIlen\fR \fR
.ad
.RS 12n
Length (in bytes) of the memory to be mapped.
.RE

.sp
.ne 2
.na
\fB\fIprot\fR \fR
.ad
.RS 12n
A bit field that specifies the protections. Possible settings are:
.sp
.ne 2
.na
\fB\fBPROT_READ\fR \fR
.ad
.RS 15n
Read access is desired.
.RE

.sp
.ne 2
.na
\fB\fBPROT_WRITE\fR \fR
.ad
.RS 15n
Write access is desired.
.RE

.sp
.ne 2
.na
\fB\fBPROT_EXEC\fR \fR
.ad
.RS 15n
Execute access is desired.
.RE

.sp
.ne 2
.na
\fB\fBPROT_USER\fR \fR
.ad
.RS 15n
User-level access is desired (the mapping is  being done as a result of a
\fBmmap\fR(2) system call).
.RE

.sp
.ne 2
.na
\fB\fBPROT_ALL\fR \fR
.ad
.RS 15n
All access is desired.
.RE

.RE

.sp
.ne 2
.na
\fB\fImaxprot\fR \fR
.ad
.RS 12n
Maximum protection flag possible for attempted mapping; the \fBPROT_WRITE\fR
bit may be masked out if the user opened the special file read-only.
.RE

.sp
.ne 2
.na
\fB\fIflags\fR \fR
.ad
.RS 12n
Flags indicating type of mapping. Possible values are (other bits may be set):
.sp
.ne 2
.na
\fB\fBMAP_SHARED\fR \fR
.ad
.RS 16n
Changes should be shared.
.RE

.sp
.ne 2
.na
\fB\fBMAP_PRIVATE\fR \fR
.ad
.RS 16n
Changes are private.
.RE

.RE

.sp
.ne 2
.na
\fB\fIcred_p\fR \fR
.ad
.RS 12n
Pointer to the  user credentials structure.
.RE

.SH DESCRIPTION
.sp
.LP
The  \fBsegmap()\fR entry point is an optional routine for character drivers
that support memory mapping.  The  \fBmmap\fR(2) system call, when applied to a
character special file, allows device memory to be mapped into user space for
direct access by the user application.
.sp
.LP
Typically, a character driver that needs to support the  \fBmmap\fR(2) system
call supplies either an \fBdevmap\fR(9E) entry point, or both an
\fBdevmap\fR(9E) and a  \fBsegmap()\fR entry point routine (see the
\fBdevmap\fR(9E) reference page). If no \fBsegmap()\fR entry point is provided
for the driver,  \fBdevmap_setup\fR(9F) is used as a default.
.sp
.LP
A driver for a memory-mapped device would provide a  \fBsegmap()\fR entry point
if it:
.RS +4
.TP
.ie t \(bu
.el o
needs to maintain a separate context for each user mapping.  See
\fBdevmap_setup\fR(9F) for details.
.RE
.RS +4
.TP
.ie t \(bu
.el o
needs to assign device access attributes to the user mapping.
.RE
.sp
.LP
The responsibilities of a  \fBsegmap()\fR entry point are:
.RS +4
.TP
.ie t \(bu
.el o
Verify that the range, defined by  \fIoffset\fR and  \fIlen\fR, to be mapped is
valid for  the device. Typically, this task is performed by calling the
\fBdevmap\fR(9E) entry point. Note that if you are using
\fBddi_devmap_segmap\fR(9F) or \fBdevmap_setup\fR(9F) to set up the mapping, it
will call your \fBdevmap\fR(9E) entry point for you to validate the range to be
mapped.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Assign device access attributes to the mapping.  See
\fBddi_devmap_segmap\fR(9F), and \fBddi_device_acc_attr\fR(9S) for details.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Set up device contexts for the user mapping if your device requires  context
switching.  See \fBdevmap_setup\fR(9F) for details.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Perform the mapping with \fBddi_devmap_segmap\fR(9F), or \fBdevmap_setup\fR(9F)
and return the status if it fails.
.RE
.SH RETURN VALUES
.sp
.LP
The \fBsegmap()\fR routine should return  \fB0\fR if the driver is successful
in performing the memory map of its device address space into the specified
address space.
.sp
.LP
The \fBsegmap()\fR must return an error number on failure. For example, valid
error numbers would be  \fBENXIO\fR if the offset/length pair specified exceeds
the limits of the device memory, or  \fBEINVAL\fR if the driver detects an
invalid type of mapping attempted.
.sp
.LP
If one of the mapping routines \fBddi_devmap_segmap()\fR or
\fBdevmap_setup()\fRfails, you must return the error number returned by the
respective routine.
.SH SEE ALSO
.sp
.LP
.BR mmap (2),
.BR devmap (9E),
.BR ddi_devmap_segmap (9F),
.BR devmap_setup (9F),
.BR ddi_device_acc_attr (9S)
.sp
.LP
\fIWriting Device Drivers\fR
